A little note about winter warfare (arctic/subarctic) from a swedish perspective.
As someone already stated you tend to move and react slower in a snowy and cold enviroment.
But with proper training and equipment you can conduct almost any military activity in cold and snowy weather, at least down to about -30 to -40 degrees Celsius. Any colder than that and machinery becomes hard to get started and equipment break down more easily.
About hiding in the snow: as long as you insulate yourself from the snow, for exampel by putting a sleeping bag or blanket between you and the snow it actually helps to keep you (relatively) warm, at the very least it protects you from the wind.
For an observation post, you would usually dig a hole in the snow, cover the bottom with something to lie/sit on, then cover the hideout with a white IR-protective camo-net.
Such an hideout could also be used for an ambush or as a machine gun nest.
I have done my share of crawling/skiing/walking in the snow during my military service in the Swedish Army.
I served in an engineer battalion stationed in the northern part of Sweden, we frequently trained north of the arctic circle.
As far as snow in Flashpoint goes, I believe that you could do as nephilim stated and use same trick as with the swimming pool. You probably could use the rotor wash scripts from some helo to simulate blowing snow and so on...